Abstract: The effect of multidirectional shaking on the liquefaction of saturated sands is estimated using the results of multidirectional shaking table tests that measured the settlement of dry sand and a model of the mechanism of liquefaction of saturated sands that uses data obtained in cyclic simple shear tests on dry sand. It is shown that excess pore pressures may develop twice as fast under two equal horizontal components of motion than is the case under a single component, but that a reduction of only 10% in the shear stresses causing liquefaction is normally adequate to account for the effect of multidirectional shaking in analyses of liquefaction potential.